Snap-acting device



1934- J. A. SPENCER 1,968,969

9 SNAP ACTING DEVICE Filed April 4 1952 2 Sheets- Sheet 1 Aug. 7, 1934. .1. A. SPENCER SNAP ACTING DEVICE Filed April 4, 1932 2 Sheets-Sheet 2 FIG. 6.

Patented Aug. 7, 1934 SNAP-ACTING DEVICE John A. Spencer, Newtonville, Mara, assignor General Plate Company, Attieboro, Mass., at corporation of Massachusetts Application April 4, 1932, Serial No. 802,907

12 Claims. (Cl. 297-15) This invention relates to snap-acting devices, and with regard to certain more specific features, to snap-acting, or overcentering devices, particularly thermostats composed preferably of composite metal.

Among the several objects of the invention may be noted the provision of a snap-acting device, which has an increased amount of displacement between its two positions; a snap-acting device of the class described which is radially corrugated and which is provided with means for eifeeting a more accelerated snap action; a snapacting device of the class described which is adapted to be held under improved conditions in a variety of mountings; a snap-acting device constituting in one embodiment a thermostat adapted for improved use in connection with temperature controlled valves, electrical switches, etc.; and the provision of a device of the class described which is economical in manufacture and simple and positive in .action. Other objects will'be in part obvious and in part pointed out hereinafter.

The invention accordingly comprises the ele- 5 ments and combinations of elements, features of construction, and arrangements of parts which ,will be exemplified in the structure hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings, in which are illustrated several of various possible embodiments of the invention,

. Fig. 1 is a plan view of a snap-acting device embodying the invention;

Fig. 2 is a side elevation of the deviceshown in Fig. 1;

Fig. 3 is a cross-section taken substantially on line 33 of Fig. 1;

Fig. 4 is a view similar to Fig. 1, showing an 40 alternative embodiment of the invention;

Fig. 5 is a view similar to Fig. 2, but pertaining to the Fig. 4 embodiment; and,

Fig. 6 is a view similar to Fig. 3, but pertaining to the Fig. 4 embodiment.

Similar reference characters indicate corresponding parts throughout the several views of the drawings.

In my Patent No. 1,895,590, dated January 31, 1933, for snap-acting devices (application for 0 which was filed June 26, 1930, and which was thus copending herewith), I have shown an improved form of snap-acting device which includes as a feature, radial corrugations, whereby an increased amount of resilient material is present in the region where displacements take place under change from one to another position. The present invention comprises an improvement over the radially corrugated device illustrated in said patent.

The invention will be described principally by 0 reference to its thermostatic embodiment, that is, where it performs in response to temperature changes. However, it will be understood that, even as a thermostat, the device is fundamentally a snap-acting device. 05

Referring now more particularly to Fig. 1, there is illustrated at numeral 1, the interior, dished or cup or concave radially corrugated region comprising the operative portion of a thermostatic embodiment of the present inven- 10 tion. This portion 1 is preferably formed from a seamless cylinder of composite thermostatic metal, briefly by, longitudinally corrugating a cylinder of thermostatic metal and then constricting said corrugated cylinder at one end as well as compressing it longitudinally until substantially a truncated cone or dished disc is obtained.

The term composite thermostatic metal is used herein to define a material composed of materials havingrelatively difl'erent coefllcients of thermal expansion. This type of thermostat is frequently termed .bimetallic'h The principle upon which the thermostat operates is that, under varying conditions 0! hot and cold, one layer of the composite metal will exhibit a relatively greater or less tendency to expand than the other layer, and thereby build up a stress in the. body which the two metals form. v

The stress thus set up grows with increased 'temperature until strains are effected whereby the disc reverses curvature with a snap. That is,

if the disc or dish or the like was originally concave, relative to its original confirmation it becomes convex, or vice versa.

The radial corrugations in the present thermostat,'as in the thermostat of said copending application, are advantageous in that they provide an increased. amount of thermostatic metal in the central portion of said disc, and, when the 10 thermostatis brought to a condition in which it is about to snap, it eifects an increase in the amount of displacement through which the center of the thermostat operates. This increased displacement is highly advantageous when the thermostat is utilized, for example, in electrical. equipment, for making and breaking electrical contacts.

The present invention comprises the formation of a radially corrugated'disc such as illustrated in my copending application, and the provision thereon of a confining annular rim or circumferential portion 3. A thermostat produced according to the present invention has the following advantages:

First, the inherent tendency of the thermostat to expand radially, and thereby to decrease its kinematic eiiiciency, is limited and controlled by the relatively non-expansible rim or confining portion 3. That is, with thermostats of the type shown in said copending application, there is a tendency upon heating for straightening of the sinuous edge, with the result that the constrictive function of the periphery is reducedas snap action occurs. Hence the thermostat functions more sluggishly than if the edge were to maintain a more constant restrictive characteristic. The relatively inexpensibIe rim portion 3 of the present invention, having no corrugations therein, has substantially no tendency to stretch, and it accordingly better serves as a restricting or confining or binding means for the remainder of the thermostat. That is to say, there are no undulations in the periphery to provide resiliency.

Second, the fiat rim 3 provides more adequate facility for mounting said thermostat, for the reason that the rim 3 is not originally formed with any sinuous curvature, and accordingly does not substantially change its shape as the thermostat changes from hot to cold position. Further, it is inherently more simple to hold a fiat surface than to hold a corrugated surface.

It will be apparent that the present invention has many other uses and applications. For example, the substantially fiat rim or edge of the present invention permits its use in valves, where it can be connected with suitable valve closure means to eifect a quick starting and stopping of flow. Other uses will also be apparent.

It is to be understood that I am aware that a substantially fiat rim has a slight capacity to stretch but it is to be noted that such capacity is much less than the corresponding capacity in an undulatory or sinuous rim. In the case of the fiat rim the stretch effects only a tensile stress, whereas in the undulatory rim a bending moment is effective. My improvement comprises arranging the metal in the periphery so that it is not subjected to bending moments and hence is much more constrictive in its action. Hence the improved increased speed attained in the snap action. It is to be understood that the invention refers broadly to binding rims of the class set forth or analogous ones performing the same functions, as claimed in. Patent No. 1,895,591.

The present application covers particularly thatembodiment of the invention wherein the binding rim is an independent piece.

Figs. 4, 5, and 6 illustrate an alternative embodiment of the invention wherein the rim 3 is replaced by a peripherally confining wire or the like 4. This embodiment is perhaps more simple of construction and/or assembly, and finds ready use where no peripherally fiat means is needed for mounting the thermostat. Its operation is not dissimilar from that of the embodiment first described.

If the invention is to be employed as a simple mechanical snap-acting or overcentering device, or spring, it will readily be seen that the use of composite thermostatic metal is unnecessary, although possible. In such instances, a single sheet of resilient metal may be used with success. The action of the device as an over-centering element needs no further description, as it varies from the thermostatic element only in that applied exthe scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. A thermostatic unit comprising a disc of composite thermostatic material, said disc being provided in the central portions thereof with radial corrugations, and at the periphery thereof with a separate binding rim.

2. A thermostatic unit comprising a disc of composite thermostatic material formed of at least two materials 0! dlil'ering coefficients of thermal expansion, said disc being radially corrugated, and an independent rim confining the periphery of said disc.

3. A thermostatic unit comprising a radially corrugated sheet of composite thermostatic material, said sheet being provided with a separate annular confining rim of non-radially corrugated material.

4. A thermostat comprising a sheet of composite thermostatic metal, corrugations therein and means for confining expansion along said corrugations, said means comprising a separate confining rim enclosing said corrugations.

5. A thermostat comprising a sheet of composite thermostatic metal, corrugations therein and means for confining expansion along said corrugations comprising at least one separate rim element positioned counter tothe corrugations, said corrugations being radially arranged and said element being circularly arranged at the periphery of said sheet.

6. A thermostatic unit comprising a disc of composite thermostatic material, said disc being provided in the central portions thereof with radial corrugations, and at the periphery thereof with a confining wire rim.

7. A thermostatic unit comprising a disc of composite thermostatic material formed of at least two materials of differing coefllcients of thermal expansion, said disc being radially corrugated, and a confining wire arranged at the periphery of said disc.

8. A thermostatic unit comprising a radially corrugated sheet of composite thermostatic material, said sheet being provided with a confining wire around its periphery.

9. A thermostat comprising a sheet of composite thermostatic metal, corrugations therein and means for confining expansion along said corrugations, said means comprising a wire.

10. A thermostat comprising a sheet of composite thermostatic metal, corrugations therein and means for confiningexpansion along said corrugations comprising at least one wire positioned counter to the corrugations, said corrugations being radially arranged and said wire being circularly arranged at the periphery of said sheet.

11. A snap-acting device comprising a disc of 145 resilient material having radial corrugations therein, the plane of the central portion of said disc being displaced from'the plane of the peripheral portion thereof, the said disc being suitably resilient, whereby upon suitable actuation 150 disc being displaced from the plane of the pe 7 ripheral portion thereof, the said disc being suitably resilient, whereby upon suitable actuation thereof, it over-centers to assume a position of opposite configuration, and a separate binding rim positioned around the outside periphery of said. disc, said rim comprising a confining wire.

JOHN A. SPENCER. 

